Background: Diacylglycerol (DAG) oil is a natural component of various edible oils. DAG has been reported to prevent obesity through a variety of potential mechanisms in comparison with triacylglycerol (TAG) in humans. An increase in postprandial energy expenditure (EE) is proposed to be one of the mechanisms underlying this effect of DAG. Up-regulated mRNA expressions associated with EE by DAG in the small intestine may explain increased postprandial EE. The small intestine seems to contribute to changes in EE by DAG. We previously studied plasma serotonin, which is mostly present in the small intestine and mediates sympathetic thermogenesis. We found that DAG ingestion increases plasma serotonin levels by approximately 50% compared to TAG ingestion.

Objective: To understand the molecular mechanisms for DAG-induced increase in serotonin and EE, we investigated effects of DAG on serotonin release and expressions of genes associated with EE, using the human intestinal cell line.

Results: 100 mM 1-MOG significantly increased serotonin release from the Caco-2 cells compared with the same concentration of 2-MOG by approximately 37% (P<0.001). Expressions of mRNA of ACO, FAT, and UCP-2 were significantly higher in 100 mM 1-MOG-treated Caco-2 cells than 100 mM 2-MOG-treaed cells by approximately 13%, 24%, and 35%, respectively. Expressions of mRNA of ACO, MCAD, FAT, and UCP-2 were significantly increased in 400 nM serotonin-treated Caco-2 cells as compared with the Caco-2 cells incubated without serotonin by approximately 29%, 30%, and 39%, respectively.

Conclusion: Our study demonstrated that a hydrolytic product of DAG increases serotonin release from the intestinal cells and enhances expressions of genes associated with b-oxidation (ACO, MCAD), thermogenesis (UCP-2) and fatty acids metabolism (FAT). Furthermore, this study revealed that serotonin also enhances expression of these genes, proposing a new molecular biological mechanism for DAG-mediated anti-obesity effect. Serotonin may play an important role in DAG-mediated prevention of obesity.

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ABSTRACT

Healthcare costs in industrialized countries are soaring as a result of rising average life expectancies and epidemics of specific chronic diseases. As the public pursues ways to become healthier and improve quality of life, functional food science has become an intriguing field of research and topic of debate to combat certain chronic diseases cost-effectively. While steps are being taken to develop and research functional food consistently across the globe, there is still not a shared international or conclusive definition of functional food. The term “functional food” was first coined in Japan in the 1980’s and the science expanded to EU and the United States quickly. However, the term “functional food” has since been the center of confusion in scientific and consumer discussions due to shifting definitions. Inconsistent definitions in the literature and government legislation have posed challenges for the development of functional food science and have caused public doubt in the effectiveness of functional food as a potential strategy for chronic diseases.

Here, the Functional Food Center’s new definition for “functional foods” was revised to: “Natural or processed foods that contains known or unknown biologically- active compounds; which, in defined, effective non-toxic amounts, provide a clinically proven and documented health benefit for the prevention, management, or treatment of chronic disease” [1,2]. In this latest version of our definition, we added the phrase “in effective non-toxic amounts” to highlight the significance of bioactive compound dosage in the consumption of functional food. This new definition of functional food by the Functional Food Center can improve communication and collaboration between the scientific, medical communities, food industry, and the public to legitimize functional food science globally.

References:

Danik M. Martirosyan and Jaishree Singh, A new definition of functional food by FFC: what makes a new definition unique? Functional Foods in Health and Disease 2015; 5(6):209-223